Help - 1992 Silverado dead in the water

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Ursus 22 years ago

Please give me some ideas on what else to test.

This is a 1992 Silverado 1500 with a 6 cyl engine. It's got 300,540 miles on it & has been a fantastic truck. I've never had a lick of electrical problems with this rig.

I cranked it up this morning & left it running for about 10 - 15 minutes ( for my wife). I turned it off. About 30 minutes later my wife went out to go to the doctor's and she said she heard a weird noise & it would not crank. She said it wasn;t a pop.

When I turned the key on, all the gauges went wacky, panel lights were flickering - all hell had broken loose. I put a meter on the battery terminals and measured only 9.8V. I disconnected the battery and measured 12.75V on the battery. I ohmed out every fuse I could find, all of them in the fuse block under the steering column & all of them under the hood (next to the coolant reservoir). All were OK.

I connected my battery charger directly to the battery leads & set it on a

10A charge. It still would not crank. Same crazy stuff with gauges and buzzers, etc. I measured 12.6V at the battery teerminals, but I did some spot measuring of voltages at connectors under the dash. I was seeing everything from 7.2V to 9.8V. That can't be right.

I don't have any schematics, so I'm taking stabs in the dark.

Can anyone offer advice on what may be the problem, or a good source for a schematic?

The only electrical work done recently was done this past Xmas. I had a new stereo system put in. Back in Feb my drivers side turn signal quit working, it was just the bulb. I have a sneakin suspiscion the folks that put in the stereo may have screwed something up.

Thanks, WS

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TranSurgeon 22 years ago

check all connections to battery and the cables

you've got a loose or corroded connection somewhere

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Steve W. 22 years ago

Bad alternator diode. Shorting power through it. Unhook the red power wire off the post on the back of the alternator to check it. Could also be a stuck solenoid on the starter that is drawing the power down.

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Wrench-head 22 years ago

Does it have tilt steering? If so, check the wires where they flex on the column. Sometimes the wires will rub on the metal dash support and ground out.

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Ursus 22 years ago

Is this diode external to the alternator (can you see it)? I disconnected the red lead from the alternator and measured the resistance. ( forward biased = very low resistance/reverse biased = very high resistance) both to the post on the alternator and to the red lead. I have 1.8 ohms (virtually a short). That threw me for a loop. I should get very high resistance at both points. I should add that I have the battery out of the circuit. I then measured across the battery leads - 1.8ohms.

So I guess I have a short between power & ground, but without a schematic I don't know where to start isolating sub-circuits or components.

Thanks for your thoughts. I should've checked for a short between power & ground from the get go.

WS

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bobo 22 years ago

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Steve W. 22 years ago

Nope. The diodes are all inside the alternator and unless you have a resistance welder you cannot replace them easily anyway. BUT you could just unbolt the unit and take it to be tested.

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TranSurgeon 22 years ago

I agree

It's almost always ONE THING, such as a bad connection or failed alternator

disconnected

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Ursus 22 years ago

You're right - I was reading way too much into this! I picked up a Haynes & Chilton manual to get a schematic & more details. The Haynes manual is the one that helped me fix this problem. It just said to measure the battery in-circuit with the key in the START position - if you measure less than

9.6V ( I was reading 9.3V), then the battery needs to be load tested. It stated you can't load test correctly with out a pile type load. So I hauled it into my friendly local parts house & they load tested it. Damn thing was no good. It was only 15 months old (72 month battery)! I slapped a new battery in there & took my truck back to the parts house so they could check my alternator. It was putting out 13.8V.

Thanks for everyone's input.

Just a comment on the manuals; The Chilton's had information the Haynes didn't have and vice-versa, so having both was very helpful. The Chilton's technical illustrations were terrible IMHO, because they were small, only about 2.5" square. They were almost useless.

Now onto the next problem -fixing the gas gauge. The dealership where I purchased the truck wants $430 for the sender unit (and that doesn't include a fuel pump)! I checked JC Whitney website & found a replacement for $229. It's on to the slavage yards form here.

disconnected

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Help - 1992 Silverado dead in the water

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